I found that my seating depth varied due to the Winchester FMJ bullet jackets actually deflecting a little. Or, at least that's what I think was happening. My seating depth was all over the map (+- .01 or worse). Tried a few other bullet types and they all loaded very consistently within a few thousandths of an inch. I probably could have corrected the problem by using a seating die with a more contoured nose punch but I've managed to use most all of those Winchester bullets just by loading long and frequently spot checking OAL.